Year 7 Science · Unit 1 · Lesson 2
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Learning Goals
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
1. The 3-domain system replaced the 5-kingdom system, so kingdoms are no longer used.
Correct it:
2. Genus is the rank directly above species.
Correct it:
3. A kangaroo and a gum tree are in the same domain but in different kingdoms.
Correct it:
4. The cells of bacteria have a nucleus.
Correct it:
5. Knowing an organism’s group lets scientists predict some of its features before they check.
Correct it:
1. Who invented the two-word naming system for species, and in what year did he publish it?
Order the ranks for the red kangaroo
Number the ranks from 1 (the biggest group) to 7 (the smallest group).
| Order (1–7) | Rank and the red kangaroo’s group |
|---|---|
| Order: Diprotodontia | |
| Species: rufus | |
| Kingdom: Animalia | |
| Genus: Osphranter | |
| Class: Mammalia | |
| Family: Macropodidae | |
| Phylum: Chordata |
2. Use the table to write the red kangaroo’s binomial name as you would by hand. Which two ranks make up the name?
Compare the two systems
Complete the table.
| Question | 5-kingdom system | 3-domain system |
|---|---|---|
| How many groups at the top level? | ||
| Where do single cells with no nucleus go? | ||
| Where do animals, plants and fungi go? | ||
| What evidence split the old Monera group? | Not split |
Read the data: a microbe survey
Scenario: five microbes
A team collects single-celled microbes from five places. They check each one for a nucleus, then compare its DNA with known microbes.
| Microbe | Where found | Nucleus? | DNA is closest to |
|---|---|---|---|
| 1 | Tub of yoghurt | No | known bacteria |
| 2 | Hot spring at 90 °C | No | known Archaea |
| 3 | Garden pond | Yes | known protists |
| 4 | Very salty lake | No | known Archaea |
| 5 | Garden soil | No | known bacteria |
Source: made-up survey results for this worksheet.
3. Name the domain of each microbe, 1 to 5.
4. Which microbes would once have shared one kingdom? Use the DNA column to explain why they now sit in two different domains.
5. A scientist in England and a scientist in Australia each write a report about “the magpie”. They are writing about two different birds: the Eurasian magpie, Pica pica, and the Australian magpie, Gymnorhina tibicen. Explain why scientists use binomial names instead of common names. Use this example and at least two rules of binomial naming.
True or false
1. False: domains are a level above kingdoms; both systems are used. 2. True. 3. True. 4. False: bacteria cells have no nucleus. 5. True.
Question 1
Carl Linnaeus (1), in 1758 (1). [2 marks]
Order the ranks for the red kangaroo
Reading down the table as printed, the correct step numbers are 4, 7, 1, 6, 3, 5, 2. In order: Kingdom Animalia; Phylum Chordata; Class Mammalia; Order Diprotodontia; Family Macropodidae; Genus Osphranter; Species rufus.
Question 2
Osphranter rufus, underlined, with a capital O and a lowercase r (1). The genus and the species (1). [2 marks]
Compare the two systems
Top level: 5 kingdoms; 3 domains. No nucleus: all in Monera; split between Bacteria and Archaea. Animals, plants and fungi: Animalia, Plantae, Fungi; all in Eukarya. Evidence: DNA, showing some microbes without a nucleus are very different from bacteria. [4 marks: 1 per row]
Read the data: a microbe survey
3. 1 Bacteria; 2 Archaea; 3 Eukarya; 4 Archaea; 5 Bacteria. [2 marks: 1 for four correct, 2 for all five]
4. Microbes 1, 2, 4 and 5, which have no nucleus, were all in Monera (1). Their DNA shows 2 and 4 are very different from 1 and 5 (1), so 2 and 4 are in Archaea and 1 and 5 in Bacteria (1). [3 marks]
Question 5
Marking guide: 1 “magpie” means different birds in different countries, so the reports could be confused; 1 each binomial name belongs to one species only, so the two birds cannot be mixed up; 1 genus first, with a capital (Pica, Gymnorhina); 1 species second, all lowercase (pica, tibicen), both words in italics or underlined; 1 the names are Latin and used by scientists everywhere, whatever their language; 1 so scientists can share information about the right species. [6 marks]
Model answer: “Magpie” means a different bird in England and in Australia, so a reader could think both reports are about one animal. Each species has only one scientific name: Pica pica in England and Gymnorhina tibicen in Australia. The genus comes first with a capital letter, the species second in lowercase, and both are in italics. Because scientists everywhere use the same Latin names, everyone knows exactly which species a report is about.
Common error: thinking domains replaced kingdoms; domains sit above kingdoms.